Showing papers by "Soteris A. Kalogirou published in 2016"

Indirect Solar Desalination (MSF, MED, MVC, TVC)

Abstract: Solar-powered desalination comprises all methods that use the sun’s energy indirectly by means of solar collectors. All solar-driven desalination processes, except solar distillation, can be fired indirectly by solar energy. In this chapter the combinations of solar thermal desalination devices to solar concentrating collectors are explained. It concerns medium to large desalination and solar plants. Initially the various types of solar collectors of large solar concentrating fields are shortly described so that the reader can have a general view of the solar concentrating plants that transform solar radiation into thermal energy. Some specific definitions and nomenclatures are described, to help the reader understand what the solar concentrators and the desalination distillation plants are. Factors that are of importance and affect the selection of the type of the two plants, for the optimum efficiencies of both systems and for the higher water productivity, are given. These determine the suitability of these combinations. Various types of solar collectors are shortly described. They include all types of solar flat-plate collectors up to point focus and heliostats for central receiver systems. The conventional desalination thermal systems, that is, conventional distillation methods, types and configurations of the corresponding evaporators, such as multiple effects distillation, multistage flash, mechanical vapor compression, and thermal vapor compression, and the variations in construction are presented for large capacity installations. For each conventional distillation method, the mathematical equations, concerning heat transfer conditions and heat balance of the system, are briefly depicted. Diagrams of temperature distribution are also given. For economic reasons, the combination of electricity production by the solar plant with hybrid and/or conventional evaporators is of importance to achieve optimum performances, as high-pressure steam from a solar collector field can be used for electricity production and waste, and low-temperature heat for the desalination plant.

Nontracking solar collection technologies for solar heating and cooling systems

Abstract: This chapter presents a review of nontracking solar thermal collectors. These collectors are suitable for low to medium temperature applications with a maximum of about 150°C. This range of temperatures is particularly suitable for solar heating and cooling applications. Usually these collectors collect both direct and diffuse solar radiation, so they are very effective collection devices. For this purpose there is no requirement to follow the sun trajectory during the day so they belong to the nontracking collectors. Some of the types presented may require seasonal tracking, ie, changing the tilt angle of a collector a few times per year. The frequency of tracking increases with the concentration ratio. Higher concentration ratio leads to higher collector operating temperature but also to higher tracking accuracy requirements. The types of collectors examined in this chapter are the flat plate collector, which is the most used collector type, and its variations, the diffuse reflector, reverse flat plate collector, compound parabolic collector, and evacuated tube collector.

Solar Distillation—Solar Stills

Abstract: This chapter is the most extended part of this book and is dedicated to solar distillation. Solar distillation was known from the antiquity as a possible way to extract fresh water from the seawater and was used in ships crossing Mediterranean Sea, in a very primitive way. A variety of configurations of solar stills are developed and tested the use of which started almost after Second World War and still today new configurations continue to be under development and improvement. Solar stills are small devices that provide a few liters of fresh water per day and are very popular in small and poor communities in Africa and other remote places. In this chapter, the most important types of solar stills and the trials made to increase their efficiency and decrease their thermal losses are described. Initially, a short description of the specific terms and definitions that govern the construction and the operational variety of the stills is given. The parts from which solar stills are assembled, including construction and operation details are also described. Special care is given on the materials that can be used, as fresh water must not contain harmful elements, which are dangerous for health and must not be expensive. The precautions that must be taken are also described in order to avoid early damage or low efficiencies of the devices. Rain water collection, if is available, can double the production of the solar still during raining days by applying inexpensive canals around the still.

Desalination Methods and Technologies—Water and Energy

Abstract: Desalination is increasing tremendously every year in fresh water production capacity as more fresh water is needed for communities, industries, and human population especially in dry regions. Many methods exist to transform sea- and brackish water or even polluted water into fresh water suitable for any use.

Building-Integrated Solar Thermal Systems

Abstract: With buildings accounting for 40 % of primary energy requirements in the EU and the implementation of the Energy Performance of Buildings Directive, developing effective energy alternatives for buildings is imperative. The increasing role for renewables implies that solar thermal systems (STSs) will have a main role as they contribute directly to the heating and cooling of buildings and domestic hot water. Meeting building thermal loads will be primarily achieved through an extensive use of renewables, following standard building energy-saving measures. These systems are typically mounted on building roofs with no attempt to incorporate them into the building envelope creating aesthetic challenges, space availability issues, and envelope integrity problems. This chapter aims to give a survey of possible solutions of STS integration on the building roofs and facades. The advantages of integration are quantified, and suggestions are given to address the possible problems created.

Water, the Raw Material for Desalination

Abstract: Seawater or brackish waters are the raw materials used in all desalination processes to obtain fresh usable water. Beginning in 1950, when industrial desalination applications started, many papers concerning sea- and brackish-water chemical, physical, and thermodynamic properties necessary for the proper operation of desalination plants were issued. These properties were available in the ranges of temperatures that the desalination plants operated. At about 2008 the Oceanographic Institutes and Committees, as IASPO, IOC, SCOR, etc., started rearranging all seawater properties in order to create more correct and accurate values. They established new seawater standards, thermodynamic equations, new numerical values, and many more. In this chapter, the new values of properties and the new equations for calculating these water properties are adopted both for seawater and for natural and desalinated water.